This application is based upon French Patent Application No. 01.16965, filed Dec. 19, 2001, the disclosure of which is hereby incorporated by reference thereto in its entirety, and the priority of which is hereby claimed under 35 U.S.C. xc2xa7119.
1. Field of the Invention
The invention relates to a sub-assembly provided to make a gliding board, particularly a board for gliding on water, such as a surfboard float.
The invention also relates to a method for manufacturing such sub-assembly, and a gliding board made from such sub-assembly.
2. Description of Background and Relevant Information
Conventionally, a surfboard float is made from a foam blank, particularly a polyurethane foam, which is formed in a mold. The foam blank is machined by planing and sanding over a low thickness to locally customize its shape, then it is coated with an envelope made of resin-impregnated fiberglass that forms an outer reinforcement shell and gives the float its final form. Decorating and glassing give the float its final aspect.
In certain cases, the foam blank is longitudinally cut in two sections that are then glued against a wooden stringer that reinforces its structure and imparts to it a predetermined longitudinal camber.
The drawback to such a constructional technique is the weight of the final float. Indeed, the foam is relatively dense, its typical density is 50 kg/m3. And theoretically, it is not possible to decrease the density of the foam without negatively affecting the mechanical properties of the float.
According to another constructional technique originating from windsurfing, one starts with a foam blank having a relatively low density (for instance, 18 kg/m3) which is machined to shape. This blank is covered with a skin made of resin-impregnated fiberglass. An envelope of foam having a higher density is attached around this sub-assembly. Then, one applies webs of resin-impregnated fiberglass in order to form the outer shell.
Such a constructional method allows for a weight reduction of approximately 20% or more while maintaining a good rigidity underfoot. However, its implementation is relatively complex. In addition, the central foam blank is usually made of expanded polystyrene foam. This material has the defect of taking in water. During its lifetime, the float may be thrown against a reef or a rock. If the outer shell is damaged, one runs the risk of water infiltrations, the water weighing down the float and being rather difficult to evacuate.
Lastly, it is known to make hollow floats having sandwich skins. Either one makes two half-shells that are then assembled together, or one makes the assembly in a closed mold with an inner bladder that is inflated in order to push and press the sandwich skins against the walls of the mold. In any case, these types of floats have walls of constant thickness.
This manufacturing technique provides results in the production of light-weight boards. However, it is not possible to customize the form of the float. In this case, the form of the outer shell depends exclusively on the form of the mold.
According to the invention, an improved sub-assembly is provided which enables the manufacture of lighter-weight gliding boards, ones that have a greater volume for an equal weight, while maintaining a form that can be customized.
More particularly, according to a method of the invention, a structural sub-assembly for a gliding board is manufactured by a method that includes the following:
forming two half-shells;
assembling the two half-shells by means of an adhesive resin foam.